1. Field of the Invention
The present invention relates to an image processor and a method therefor, and an image display device. The invention particularly relates to those that receive an image having high spatial-frequency components.
2. Description of the Prior Art
In projection-type display devices such as rear projection televisions, image distortion such as keystone distortion arises from positional relation between the screen and the light emitting source, or image distortion arises from an aberration of an optical system. In order to correct such distortion, known are methods of projecting an image having been inversely transformed according to the distortion characteristic.
Among the methods, there is one that generates an image having an inverse distortion characteristic by processing its image signal, and a liquid crystal projector employing the method is proposed that corrects a keystone distortion by changing the number of pixels in a scan line on a predetermined scan-line number basis (refer to, for example, Japan Patent Application Laid-Open No. H08-102900 (paras. [0021] and [0027], and FIGS. 2 and 3).
However, in a case of magnifying or reducing an image with the number of pixels varied in accordance with the above-mentioned manner, for example, when an input image contains a larger magnitude of high frequency components, moiré is generated in its output image owing to an aliasing distortion caused by resampling the original image at a transformed pixel position, resulting in a problem with deterioration of image quality.
A method may generally be employed that prevent moiré from appearing by smoothing an image signal without taking into account the distribution of frequency components contained in the image data. Using the method, however, even a fine pattern or the like unrelated to the moiré becomes blurred, resulting in a problem with deterioration of image quality.